Emission Control System: Purpose
WARNING: This page is about a different car, the 2004 Lexus LX 470. However, it is still accessible from the selected car via links, so may be relevant.
The emission control systems are installed to reduced the amount of HC, CO and NOx exhausted from the engine ((3) and (4)), to prevent the atmospheric release of blow-by gas-containing HC (1) and evaporated fuel containing HC being released from the fuel tank (2).
The function of each system is shown in the Fig 1 .